https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116417
Bug ID: 116417
Summary: SFINAE on std::is_destructible cannot handle
destructor of scalar type
Product: gcc
Version: 14.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: amy at amyspark dot me
Target Milestone: ---
Hi all,
I have the following test case that compiles in Clang 20.0.0 commit
7d5281a66d5d42c65cfb9d95eaf9aa01afb089fb :
```c++
#include <type_traits>
namespace _impl {
template<typename _Ty, typename =
decltype(std::declval<_Ty&>().~_Ty())>
constexpr auto _try_is_destructible(int) -> std::true_type;
template<typename>
constexpr auto _try_is_destructible(...) -> std::false_type;
}
template<typename _Ty>
struct is_destructible : std::conditional_t<
!std::is_void_v<_Ty> && !std::is_unbounded_array_v<_Ty> &&
!std::is_function_v<_Ty>,
std::conditional_t<
std::is_reference_v<_Ty>,
std::true_type,
decltype(
_impl::_try_is_destructible<std::remove_all_extents_t<_Ty>>(0)
)
>,
std::false_type
> {};
template<typename _Ty>
inline constexpr bool is_destructible_v = is_destructible<_Ty>::value;
static_assert(is_destructible_v<int&>);
int main(int, char**) {
return 0;
}
```
GCC 14.1 refuses to build with the following error:
```
<source>: In substitution of 'template<class _Ty, class> constexpr
std::true_type _impl::_try_is_destructible(int) [with _Ty = int&;
<template-parameter-1-2> = <missing>]':
<source>:17:63: required from 'struct is_destructible<int&>'
17 |
_impl::_try_is_destructible<std::remove_all_extents_t<_Ty>>(0)
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
<source>:24:65: required from 'constexpr const bool is_destructible_v<int&>'
24 | inline constexpr bool is_destructible_v = is_destructible<_Ty>::value;
| ^~~~~
<source>:26:15: required from here
26 | static_assert(is_destructible_v<int&>);
| ^~~~~~~~~~~~~~~~~~~~~~~
<source>:4:74: error: 'std::declval<int&>()' is not of type 'int&'
4 | template<typename _Ty, typename =
decltype(std::declval<_Ty&>().~_Ty())>
|
~~~~~~~~~~~~~~~~~~~~~~^~~
ASM generation compiler returned: 1
<source>: In substitution of 'template<class _Ty, class> constexpr
std::true_type _impl::_try_is_destructible(int) [with _Ty = int&;
<template-parameter-1-2> = <missing>]':
<source>:17:63: required from 'struct is_destructible<int&>'
17 |
_impl::_try_is_destructible<std::remove_all_extents_t<_Ty>>(0)
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
<source>:24:65: required from 'constexpr const bool is_destructible_v<int&>'
24 | inline constexpr bool is_destructible_v = is_destructible<_Ty>::value;
| ^~~~~
<source>:26:15: required from here
26 | static_assert(is_destructible_v<int&>);
| ^~~~~~~~~~~~~~~~~~~~~~~
<source>:4:74: error: 'std::declval<int&>()' is not of type 'int&'
4 | template<typename _Ty, typename =
decltype(std::declval<_Ty&>().~_Ty())>
|
~~~~~~~~~~~~~~~~~~~~~~^~~
Execution build compiler returned: 1
```
Looks like it's been found and worked around before, but no report has been
filed: https://stackoverflow.com/a/53458189
Godbolt here: https://godbolt.org/z/Edes1sjzo
